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1
Xu, Qingyun, Jian-Biao Bai, Shuai Yan, Rui Wang, and Shaoxu Wu. "Numerical Study on Soft Coal Pillar Stability in an Island Longwall Panel." Advances in Civil Engineering 2021 (January 29, 2021): 1–13. http://dx.doi.org/10.1155/2021/8831778.
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Roadway support and management of longwall panels in an island soft coal panel are always difficult work. In a test mine, stress distribution, deformation characteristic, and plastic zone distribution around the roadway and coal pillars in the development and mining periods were investigated with respect to the widths of different coal pillars using theoretical and simulation methods. The most reasonable width of coal pillars was comprehensively determined, and the field test was conducted successfully. The results show that a reasonable width of coal pillars is 7.0–8.2 m using the analytical method. The distribution of vertical stress in the coal pillars showed an asymmetric “double-hump” shape, in which the range of abutment pressure was about 26.0–43.0 m, and the roadway should be laid away from stress concentration. When the coal pillar width is 5.0–7.0 m, deformation of the roadway is half that with 8.0–10.0 m coal pillar in the development and mining period. The plastic zone in the surrounding rock firstly decreases and increases with increasing coal pillar width; the smallest range occurs with a coal pillar width of 5.0 m. Finally, a reasonable width for coal pillars in an island panel was determined to be 5.0 m. Industrial practice indicated that a coal pillar width of 5.0 m efficiently controlled deformation of the surrounding rock, which was an important basis for choosing the width of coal pillars around gob-side entries in island longwall panels with similar geological conditions.
2
Sidorenko, Andrey, Vyacheslav Alekseev, and Vladimir Ivanov. "Numerical analysis of inter-panel pillars in the bump prone conditionals of the Alardinskaya mine." E3S Web of Conferences 326 (2021): 00009. http://dx.doi.org/10.1051/e3sconf/202132600009.
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The purpose of the paper is to substantiate the width of the barrier and yield pillars for the application of a new seam development scheme in the conditions of the Alardinskaya mine (Russia). The Alardinskaya mine develops gas-bearing coal seams that are prone to spontaneous combustion and are hazardous due to rock bumps, which leads to frequent accidents. The analysis of the world experience of mining seams being hazardous to rock bumps showed that safe mining with longwalls can be provided by a system of inter-panel pillars: very wide barrier pillar and two yield pillars. Numerical modeling using the finite element method was carried out to assess the possibility of reducing the barrier pillar width in order to decrease the volume of coal losses in the subsoil. The model of rock massif was created in Ansys mechanical software. Numerical modeling of the longwall panel development with longwalls was carried out at various widths of broad and yield pillars. The analysis outcomes of the vertical stresses diagrams in the seams are presented for different parts of the longwall panel. The rational parameters of the pillar system, ensuring the minimization of the reference pressure influence from the previously worked-out column and the reference pressure of the operating longwall, are determined as a result of numerical analysis. The conclusion is made about the expediency of the technological scheme application proposed by the authors in the conditions of the Alardinskaya mine to reduce the endogenous fire hazard and the danger of rock bumps.
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Jiang, Bangyou, Hongguang Ji, Long Fu, Shitan Gu, Tong Zou, and Jiaxin Lu. "Research on Evaluation Index and Application of Rockburst Risk in Deep Strip Mining." Shock and Vibration 2020 (September 8, 2020): 1–10. http://dx.doi.org/10.1155/2020/8824323.
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The practice shows that deep strip mining induces rockburst disaster easily. Accurately evaluating rockburst risk of the strip coal pillar is of great significance for ensuring the safety of deep strip mining. In this paper, the catastrophe mechanics model was used to analyze the abrupt instability condition of strip coal pillar. And the three indicators that are the medium stiffness ratio (k) of the elastic and plastic zone in the coal pillar, the plastic zone width ratio (aY), and the elastic deformation index (Uq) of core zone were put forward with considering the geometry size of coal pillar. Based on the 3202 panel of Gucheng Coal Mine, the evolution characteristics of rockburst risk of coal pillar under different mining widths and coal pillar widths were studied by numerical simulation. The evaluation result shows that the strip coal pillar of the 3202 panel is in danger of strong rockburst, which is more in line with the actual situation than the results of the traditional rockburst tendency identification test and comprehensive index method. These three indicators can be regarded as important indicators to evaluate the rockburst risk in the strip mining engineering field. Based on that, the design principle of strip mining in Gucheng Coal Mine was put forward, which is considered an important reference for similar cases.
4
Liu, Shuaigang, Jianbiao Bai, Xiangyu Wang, Bowen Wu, and Wenda Wu. "Mechanisms of Floor Heave in Roadways Adjacent to a Goaf Caused by the Fracturing of a Competent Roof and Controlling Technology." Shock and Vibration 2020 (May 19, 2020): 1–17. http://dx.doi.org/10.1155/2020/5632943.
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In traditional sequential single-wing mining practices, one-entry longwall mining systems make it challenging to efficiently and smoothly transfer mining equipment during a continuous mining sequence. In two-entry longwall systems, the headgate of the current panel and the tailgate of the next panel are excavated parallel to one another, effectively creating space for the transfer of mining equipment. The tailgate of the panel, however, is subjected to high-mining-induced stresses, causing severe floor heave, which seriously affects the efficiency of coal production. In this paper, field measurements and numerical simulation methods are used to reveal the mechanism of floor heave induced by the rupture and instability of a competent roof. The results show that the positional relationship between the adjacent tailgate and the longwall face is divided into three stages. Throughout the three stages, the area in which the coal pillar is not horizontally displaced moves from the center of the pillar to the goaf, and the area of peak vertical stress within the coal pillar shifts from the center of the pillar to the side nearest to the tailgate. Field studies suggest that the proposed technologies can effectively control floor heave in the tailgates of two-entry longwall mining systems.
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Yu, Yihe, Liqiang Ma, and Dongsheng Zhang. "Characteristics of Roof Ground Subsidence While Applying a Continuous Excavation Continuous Backfill Method in Longwall Mining." Energies 13, no. 1 (December 23, 2019): 95. http://dx.doi.org/10.3390/en13010095.
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Activities of traditional longwall mining will result in ground subsidence and therefore cause issues such as damages to buildings and farmlands, water pollution and loss, and potential ecological and environmental problems in the mining region. With advantages of the longwall backfill mining method, as well as the room and pillar mining method, a continuous excavation and continuous backfill (CECB) method in longwall mining is recommended to effectively control the ground subsidence. In this method, mining roadways (MRs) are initially planned in a panel, and then they are excavated and backfilled in several stages until the whole panel is mined out and backfilled. According to the geologic conditions of an underground coal mine, and the elastic foundation beam theory, a mechanical model was built to study the subsidence of the roof while using this new mining method. In addition, methods to calculate roof subsidence in various stages in CECB were also provided. The mechanical parameters of backfilling materials, which were used in the theoretical calculation and the numerical analysis for mutual check, were defined through analyzing the stability conditions of the coal pillars and the filling bodies. The control effect for the ground subsidence of using the newly proposed mining method was analyzed based on both simulation results and site monitoring results, including the ground subsidence, horizontal displacement, tilt, curvature and horizontal strain. This research could provide suggestions to effectively control ground subsidence for a mine site with similar geologic conditions.
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Wu, Rui, Qingyuan He, Joung Oh, Zecheng Li, and Chengguo Zhang. "A New Gob-Side Entry Layout Method for Two-Entry Longwall Systems." Energies 11, no. 8 (August 10, 2018): 2084. http://dx.doi.org/10.3390/en11082084.
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The gob-side entry layout is popular at two-entry longwall mine sites in China for the benefit of improving the coal recovery rate. Currently, two methods have been widely used to develop gob-side entries, including gob-side entry retaining and gob-side entry driving. Gob-side entry retaining maximizes the recovery rate by pillarless mining but increases the difficulty in gob-side entry support. Also, this method has limited applications in hard roof conditions. The gob-side entry driving mine site uses the rib pillar to separate the gob entry and the gob area of the previous panel, which leads to additional coal losses. The waste is more intolerable in large-cutting-height panels and longwall top coal caving panels as the Chinese government limits the minimum recovery rate of longwall panels using these mining methods. In this paper, a new gob-side entry layout method, termed gob-side pre-backfill driving, is established to overcome the shortcomings of the existing methods. The new method eliminates rib pillar losses and enhances gob-side entry stability. The feasibility of gob-side pre-backfill driving is studied by numerical modelling and a field trial at Changcun Mine in China. The results indicate that gob-side pre-backfill driving is an alternative for gob-side entry development. This method is practical and also has the potential to bring significant economic benefits to the mining industry.
7
Wang, Feng, Shaojie Chen, Jialin Xu, and Mengzi Ren. "New Method to Design Coal Pillar for Lateral Roof Roadway Based on Mining-Induced Stress: A Case Study." Advances in Civil Engineering 2018 (October 24, 2018): 1–13. http://dx.doi.org/10.1155/2018/4545891.
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The traditional method to design coal pillar for lateral roof roadway was established based on the mining-induced strata movement contour which is considered as a straight line, while ignoring the variations of the internal strata deformation law as well as stress distribution characteristics. In order to make up for this deficiency, in this study, evolution of mining-induced stress in the overlying strata was simulated using physical and numerical simulations, and a method to design coal pillar for lateral roof roadway based on mining-induced stress was proposed. The results indicate that the stress of the overlying strata is redistributed during excavation, and the stress distribution can be divided into a stress-relaxation area, a stress-concentration area, and an in situ stress area. The contour line of 1.05 times the in situ stress is used to define the mining-induced stress contour. Stress inside the contour is redistributed while outside the contour the overlying strata are still within the in situ stress area. Mining-induced stress contour presents a concave-upward type from coal seam to the overlying strata that cannot be merged into a straight one due to their different characteristics of movement and deformation. With this in mind, this study proposed a method to design the width of coal pillar for lateral roof roadway according to the mining-induced stress contour. According to mining-induced stress contour, the width of coal pillar for lateral roof roadway of longwall panel 31100 is 160 m, and the maximum deformation of the roadway is 270 mm. The new method can definitely meet engineering demands.
8
Krukovskyi, Oleksandr, Yurii Bulich, Serhii Kurnosov, Oleksii Yanzhula, and Vladimir Demin. "Substantiating the parameters for selecting a pillar width to protect permanent mine workings at great depths." IOP Conference Series: Earth and Environmental Science 970, no. 1 (January 1, 2022): 012049. http://dx.doi.org/10.1088/1755-1315/970/1/012049.
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Abstract Application of a method to protect permanent mine workings by large pillars requires thorough analysis of geomechanical processes aimed at providing stability for a mine working during its long-term operation. The purpose of the paper is to study the processes of coal rock mass deformation to substantiate the selection of the protective pillar width. The examples to be considered are represented by mining-geological conditions of a central panel of PJSC Colliery Group “Pokrovske” where four permanent mine workings are planned to be driven. To substantiate the width of protective pillars, geomechanical stability of mine workings have been assessed in terms of the effect of stoping operations of the adjacent longwalls of the block and beyond their effect. It has been shown that insufficient dimensions of a support pillar result in considerable influence of stoping operations on the stability of permanent mine workings. Along with the increasing dimensions of a support pillar, the pressure in the rocks around the permanent inclined mine workings decreases, and the support load decreases as well. In terms of the appropriate dimension of the support pillar, the boundaries of the effect become smaller; the bolting and frame support provides completely the required mine working stability.
9
Bilash Prajapati, Ram, Rabindra Kumar Sinha, R. N. Gupta, Sikandar Kumar, and Deepti Prajapati. "Artificial Intelligence Model for Prediction of Local and Main FALL in caving Panel of Bord and Pillar Method of Mining." Journal of Mines, Metals and Fuels 70, no. 4 (June 20, 2022): 171. http://dx.doi.org/10.18311/jmmf/2022/30018.
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Depillaring with caving method of mining is a common practice in Indian coalfields and so is the occurrence of fall in goaf area, which can be considered as a boon in disguise as it allows wining of coal from large reserves but this becomes a curse just because of its unpredicted occurrence. Various empirical and statistical models are developed after idealization of several complicated mechanisms but they are not able to predict roof fall accurately especially in caving panels. Therefore, a new approach based on Artificial Intelligence is used to predict the sequence of local and main fall in caving panel taking into account a host of geotechnical and mining parameters of the mine. Mathematical equations and hidden calculations of artificial neural networks are known to have the capability of learning and analyzing records endlessly. Two different models have been deployed after optimal hyper parameter optimization to predict the occurrence of fall and to characterize the nature of fall (local or main) with considerable and reliable accuracy.
10
Li, Yang, Yuqi Ren, Nan Wang, Junbo Luo, Na Li, Yikun Liu, and Guoshuai Li. "A Novel Mining Method for Longwall Panel Face Passing through Parallel Abandoned Roadways." Shock and Vibration 2021 (June 14, 2021): 1–10. http://dx.doi.org/10.1155/2021/9998561.
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Mining pressure behavior in the process of longwall panel face passing through the parallel abandoned roadways (PARs) is different from the ordinary longwall panel face. It is easy to induce the accident of roof falling, coal wall spalling, and crush accident of shield. In order to reduce the occurrence of mine pressure accidents and ensure safe mining, a new mining method named “swing-inclined” mining method was proposed and was employed in the E13103 of Cuijiazhai coal mine. Based on the process of the longwall panel face passing through the PARs, a long-span and multisupport mass-structure model of the roof was established. The maximum support capacity of shield was calculated combined with stability relation between “roof-shield-PAR-‘similar pillar (SP)’-coal wall.” It provided the basis for determining the reasonable support capacity of shield. Moreover, the sensitivity analysis of influenced factors to the maximum support capacity of shield was carried out by using Matlab software. The sensitivity analysis results indicated that different factors had a different effect on the support capacity of shield. And, the process of passing through the PARs can be divided into 3 stages, depending on the relation between support capacity of shield and width of SP. In different stages, the change degree of support capacity of shield was different. The support capacity of shield is mainly influenced by the hanging distance of the main roof and the horizontal distance between the support point of the coal wall and the breaking position of the main roof. By on-site measurement, the sensitivity analysis results were verified.
11
Nimaje, Devidas S., and Shiva Sai. "Development Of Software To Evaluate Roof Fall Risk In Bord And Pillar Method - Depillaring Phase." GeoScience Engineering 61, no. 2 (June 1, 2015): 14–22. http://dx.doi.org/10.1515/gse-2015-0014.
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Abstract Roof fall is one of the major problems of the bord and pillar coal mines during the depillaring phase. Roof fall not only causes considerable damage to the mining equipment but also to the miners. To keep in view, development of software is essential for the calculation of roof fall risk to reduce the accidents to a certain extent. In this paper, the software has been developed and tested on seam-2, the main panel of RK-5 underground coal mine, Singareni Collieries Company Limited, India and corresponding roof fall risk was calculated. The best combination of the parameters causing roof fall risk was evaluated to reduce the risk.
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Hashikawa, Hiroto, Pisith Mao, Takashi Sasaoka, Akihiro Hamanaka, Hideki Shimada, Ulaankhuu Batsaikhan, and Jiro Oya. "Numerical Simulation on Pillar Design for Longwall Mining under Weak Immediate Roof and Floor Strata in Indonesia." Sustainability 14, no. 24 (December 9, 2022): 16508. http://dx.doi.org/10.3390/su142416508.
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In Indonesia, the adoption of the underground coal mining method is discussed to extend coal production. However, the geological conditions in Indonesia are very weak. In particular, the mechanical properties of the immediate roof/floor in shallow depths are weaker than those of coal. Therefore, the control measures to maintain stability around the developing area should be discussed for safe longwall mining operations. This study discusses the design of safety pillar width in longwall mining under weak geological conditions by using FLAC3D. The study reveals that the conventional equations for the determination of the pillar width, i.e., Obert-Duvall, Holland-Gaddy, and Bieniawski equations, can be adopted to maintain the stability of the pillar itself but are not suitable for the stability of the longwall face because of the influence of the extracted neighboring panels. Additionally, the increase of the pillar width can significantly reduce the fracture zone around the longwall face. Also, increasing the setting load of the powered support can slightly improve the stability. In the pillar design, both the pillar strength and the stability of the longwall face under weak geological conditions need to be considered.
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SOKOLOV, Igor, Yury ANTIPIN, and Artem ROZHKOV. "MODERNIZATION OF THE MINING SYSTEM OF SMALL DEPOSITS OF RICH COPPER PYRITE ORES." Sustainable Development of Mountain Territories 12, no. 3 (September 30, 2020): 444–53. http://dx.doi.org/10.21177/1998-4502-2020-12-3-444-453.
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The purpose work. Substantiation and selection of a safe and effective option of mining technology of the experimental block in the pilot industrial mining of the Skalistoe deposit. Method of research. Analysis and synthesis of project solutions, experience in mining inclined low-thickness ore bodies, economic and mathematical modeling and optimization of the parameters of options mining systems in the conditions of the experimental block. Results of research. As a result of research it was established: - the sublevel caving mining system with the parameters adopted in the project does not guarantee the completeness of the extraction of reserves and the effectiveness of mining operations. Project indicators of extraction by sublevel caving technology with frontal ore drawing are overestimated and difficult to achieve in these geological and technical conditions (combination of low thickness and angle of ore body); project scheme for the delivery and transportation of rock mass seems impractical due to the significant volume of heading workings and increased transportation costs; - eight technically rational options of various mining systems were constructed, most relevant to the geological and technical conditions of the deposit. Five variants of the sublevel chamber system and pillar caving, a project variant of sublevel caving technology with frontal ore drawing and two options flat-back cut-and-fill system were considered; - for mining the Skalistoe deposit, according to the results of economic and mathematical modeling, optimal by the criterion of profit per 1 ton of balance reserves of ore is a option of the technology of chamber extraction with dual chambers, frontal drawing of ore by remote-controlled load-haul-dump machine and subsequent pillars caving, as having the greatest profit; - the calculations justified stable spans of dual chambers (25.3 m) and the width of panel pillars (3 m). With an allowable span of 25.3 m, the roof of the dual chambers will be stable with a safety factor of 1.41, and a panel pillar with a width of 3 m has a sufficient margin of safety (more than 1.6) in the whole range of ore body thickness variation; - the proposed scheme of delivery and transportation of rock mass, which allows to reduce the volume of tunnel works by 26% and the average length of transportation by 10-15% compared with the project. Findings. Developed in the process of modernization the technology sublevel chamber system with double-chamber, compared with the project technology, it is possible to significantly increase the efficiency of mining of the low thickness deposit of rich ores Skalistoe by reducing the specific volume of preparatory-rifled work by 34%, the cost of mined ore by 12%, losses and ore dilution – by 2 and 2.9 times, respectively.
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Chawla, Shailendra, Ashok Jaiswal, and B. K. Shrivastva. "Design of remnant pillar in mechanized depillaring using continuous miner." Journal of Mines, Metals and Fuels 69, no. 2 (March 15, 2021): 45. http://dx.doi.org/10.18311/jmmf/2021/27332.
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Ribs and snooks are the critical natural support at the goaf edge in the mechanized depillaring operation of the bord and pillar mining system. The pillar extraction has been carried out by taking the slices and leaving ribs and snooks during the depillaring operation. Remnants are the remaining portion of the extracted pillar. The depillaring operation leads to an unsupported roof, and the immediate unsupported roof imposes its weight on the pillar (remnant) under extraction. The remnant’s purpose is to provide a necessary reaction to the overhang to restrict roof failure until the pillar’s final slice. The remnant’s stability during depillaring operation has been accessed in the study using three-dimensional numerical simulations. A scheme has also been proposed in the study to evaluate the factor of safety (FOS*) of the remnant pillar in the residual phase at different stages of slicing operation. A case of an Indian coal mine using the fish-bone method has been chosen for the study. A typical depillaring stage has been selected for the extraction of the pillar using the fish-bone method. The numerical simulation of the considered panel provides the vertical stress and yielding profile on the pillars at different stages of depillaring. The simulation results show the influence zone up to one pillar from the goaf edge. The immediate intact pillar shows considerable yielding of about 60% of the pillar area. The remnants have completely yielded during the slicing operation but provide a reaction to the immediate strata. The remnant should provide the reaction to the immediate roof till taking the final slice from the pillar. The remnant’s FOS* is calculated by taking the ratio of reaction offered by the remnant (numerical simulations) and the weight of the overhang (estimation). The area’s borehole section shows two layers of medium to coarse-grained sandstone as an immediate stratum. The weight of the immediate strata has been estimated in the study considering the immediate strata’s thickness. Two different scenarios of immediate strata thickness (i.e., 4.75 m and 9 m) have been considered in the study to evaluate the remnant’s FOS at different depillaring stages.
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Bell, F. G., and D. D. Genske. "The influence of subsidence attributable to coal mining on the environment, development and restoration; some examples from Western Europe and South Africa." Environmental and Engineering Geoscience 7, no. 1 (February 1, 2001): 81–99. http://dx.doi.org/10.2113/gseegeosci.7.1.81.
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Abstract Coal mining has been practised in some parts of the world, notably western Europe, for centuries and this type of mining has evolved over time as mines became deeper and larger. Today coal is worked primarily by room-and-pillar, and by longwall methods. One of the consequences of mining is subsidence, and it is associated with past and present mine workings. Indeed, old abandoned coal mines worked by the room-and-pillar method, which occur at shallow depth, often present a potential hazard as pillars collapse or voids migrate to the surface. Frequently, the situation is compounded by the fact that such workings are unrecorded. Subsidence prediction in such cases is impossible. In longwall mining, the total extraction of panels takes place, the working face being supported, while support is removed from behind the working face allowing the roof to collapse. Subsidence consequent on longwall mining can be regarded as more or less contemporaneous with mining and is normally predictable. This means that it is possible to develop an area after subsidence due to longwall mining has occurred or to incorporate features into the design of buildings and structures that will accommodate ground movements generated by subsidence. The nature of subsidence can be affected by discontinuities in the surface strata or the presence of superficial deposits. Of course, subsidence can adversely affect existing buildings and structures which do not incorporate special design features. In severe cases of subsidence damage, buildings may have to be demolished. Important buildings may be restored. Another problem associated with subsidence is flooding due to notable lowering of the ground surface. Examples of such problems and solutions are highlighted by the examples given.
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Ladinig, Tobias, Horst Wagner, Markus Karlsson, Matthias Wimmer, and Michal Grynienko. "Raise Caving—A Hybrid Mining Method Addressing Current Deep Cave Mining Challenges." BHM Berg- und Hüttenmännische Monatshefte 167, no. 4 (March 11, 2022): 177–86. http://dx.doi.org/10.1007/s00501-022-01217-3.
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AbstractCave mining progresses to depths exceeding 1000 m and ore bodies situated in competent and strong rock masses are nowadays extracted by different cave mining methods. Widely applied caving methods in massive deposits are block and panel caving, inclined caving, and sublevel caving. All caving methods have in common that rock mass caves during extraction of an ore body in a controlled way. As a result, regional stress changes occur, considerable abutment stresses form, and large-scale subsidence and significant seismic energy releases occur. Experience shows that these rock mechanics effects become especially critical at great depths, where primary stress magnitudes reach and exceed rock mass strength, as well as in strong competent rock masses, which require large footprints to enable continuous caving. The presented raise caving method addresses previously mentioned rock mechanics issues. Initially, de-stressing slots are developed from raises with a minimum amount of pre-development. Substantial pillars separate neighboring slots in order to control stress magnitudes and seismicity near slots. The slots provide a stress shadow for production infrastructure so that large-scale mineral extraction can take place in de-stressed ground. As mining progresses, pillars are extracted and hanging wall is allowed to cave. Results of a pre-study conducted together with LKAB have highlighted advantages of raise caving from a rock mechanics, safety, and cost point of view.
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Dvořák, Pavel, and Eva Jiránková. "EFFECTS ON THE FINAL INTENSITY OF INPUT FORCES IN LONGBOLTS INSTALLED AT THE MINING OPERATION 2 AREA, OKD, INC." Acta Polytechnica 58, no. 5 (October 31, 2018): 279. http://dx.doi.org/10.14311/ap.2018.58.0279.
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In the deep coal mines of OKD, Inc., both bolts and long bolts of different designs are used for the rock massif and steel arch support reinforcement. Continuous measurement of forces in 6 strand bolts and 1 cable bolt (long bolts, generally) was carried out during the trial operation of the modified Room and pillar mining method at Mining operation 2, site North, OKD, Inc. Hydraulic dynamometers were installed on these long bolts and a monitoring of forces took place throughout the life-time period of the mining panel No. V. From this measurement, a knowledge of their different load behavior with respect to the input stress parameters was obtained. The input intensity of the force applied to the bolting elements is burdened by losses of various kinds. The subject of the article is a description and analysis of the intensity of the initial stressing force applied to individual long bolts (with a threaded clamping bush or wedge barrel) and quantization of short-term stress losses with a description and analysis of these.
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Wang, Qingwei, Hao Feng, Peng Tang, Yuting Peng, Chunang Li, Lishuai Jiang, and Hani S. Mitri. "Influence of Yield Pillar Width on Coal Mine Roadway Stability in Western China: A Case Study." Processes 10, no. 2 (January 27, 2022): 251. http://dx.doi.org/10.3390/pr10020251.
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Roadway excavation technology in underground coal mines has an important impact on mining efficiency and production safety. High-efficiency and rapid excavation of underground roadways in coal mines are important means to improve the production efficiency of coal mines. To tackle the problems of instability of roadway and support difficulties, the tail entry of panel 3105 in Mataihao Mine was used as the case study. The methods of underground investigation, theoretical analysis, and FLAC3D numerical simulation were used to analyze the stability of the surrounding rock under different yield pillar widths. Through the stress field, displacement field, and plastic zone of roadway surrounding rock, the stability of the rock surrounding the roadway under different yield pillar widths (4 m, 6 m, and 8 m) was analyzed. The results show that, with the increase in the yield pillar width, the plastic zone failure and displacement of the roadway surrounding rock are mainly manifested in the narrow pillar rib, seam rib, roof, and floor. The plastic zone distribution changes slightly; the roadway displacement exhibits basic symmetry. The vertical stress and the displacement of the two sides increase with the increase in the yield pillar width, and the roof displacement and the ratio of tensile failure of the surrounding rock decrease with the increase in the yield pillar width. According to the dynamic evolution law of the rock surrounding the roadway along the goaf side, the effect of the yield pillar size is revealed, and a reasonable yield pillar width is determined. When the yield pillar width is 6 m, the plastic zone failure of the surrounding rock and the displacement of the two sides of the roof are the most balanced among the three schemes. This provides a reference for the selection of the narrow yield pillar size in coal mines under the same geological conditions.
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Marian, Dacian Paul, Ilie Onica, Ramona-Rafila Marian, and Dacian-Andrei Floarea. "Finite Element Analysis of the State of Stresses on the Structures of Buildings Influenced by Underground Mining of Hard Coal Seams in the Jiu Valley Basin (Romania)." Sustainability 12, no. 4 (February 20, 2020): 1598. http://dx.doi.org/10.3390/su12041598.
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The hard coal seams in the Jiu Valley mining basin have been mined with different mining methods and technologies, including with the complete caving of the surrounding rocks and with top coal caving. These mining systems have led to the degradation of the ground surface by producing subsidence of the land, ranging from a few meters up to tens of meters, in the areas with thick coal seams with high dips. When the limits of the main safety pillars are accidentally exceeded whilst mining, buildings situated either below the ground or on the surface are affected. In the future, the possibility exists of mining some of the very large reserves that are immobilized in the main safety pillars, where the gentle dip seams are stored. In consideration of the above, in order to study the behaviour of typical buildings that are under the influence of underground mining and to develop a model of the stress state in the structural elements of the structures, finite element modelling is used. As such, several modelled buildings with one, two, and three levels were generated, as well as buildings with two levels and with different lengths. These buildings were built of reinforced concrete panels or brick masonry and were subjected to the mining influence of a panel specific to the mines in the Jiu Valley basin, sequentially extracted with a longwall coal face method at different operating heights, with the use of roof control by caving of rocks and with top coal caving methods. Following the analysis of the major principal (tensile) stresses and minor principal (compressive) stresses, a series of conclusions regarding the behaviour of these buildings that are under the influence of the underground mining is revealed. In this context, it was concluded that the value and location of the stresses developed in the structure of the buildings depend mainly on the extension of the panel and the volume of the goaf, the relative position of the building in respect to the coal face line, and the length of the building.
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Wang, Xin, Yuechao Wu, Xuehua Li, and Shun Liang. "Numerical Investigation into Evolution of Crack and Stress in Residual Coal Pillars under the Influence of Longwall Mining of the Adjacent Underlying Coal Seam." Shock and Vibration 2019 (February 17, 2019): 1–18. http://dx.doi.org/10.1155/2019/2094378.
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Longwall mining of the adjacent coal seam with the presence of residual coal pillars overlying the seam can result in abnormal strata pressure and severe overburden failure, which poses a significant threat to mining safety. The threat is mainly manifested in the form of intense coal or rock burst and hazardous interconnection between gobs. This study employed the universal distinct element code (UDEC) to investigate the microscopic failure mechanism of the overlying residual coal pillars under the influence of longwall mining of an adjacent underlying coal seam in Yuanbaowan coal mine, China. Using the Voronoi method, we innovatively visualized the evolution of cracks in residual pillars, revealed the mechanism behind the failure of pillars, and explored the evolution and distribution of abutment stress. Also, strata movement characteristics during underlying panel extraction have been surveyed. Based on the modeling results, effective measures are proposed to ensure safe mining under residual coal pillars. This study might provide a certain reference for safe extraction of multiple seams in Datong Coalfield, China, and also in the central and western Appalachian Basin, United States, where many mining activities are carried out under residual pillars.
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Golovaty, I. I., S. A. Chizhik, A. B. Petrovskiy, and V. Ya Prushak. "Development of technology for additional extraction of potash ore reserves from previously mined out panels at the depths exceeding 600 metres of the Starobin potash salt deposit." Proceedings of the National Academy of Sciences of Belarus, Physical-Technical Series 67, no. 2 (July 2, 2022): 182–90. http://dx.doi.org/10.29235/1561-8358-2022-67-2-182-190.
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Studied the possibility to extend the life of the Production Unit no. 3 mine of JSC “Belaruskali” through the additional extraction of sylvinite ore reserves left in the previously mined panels of the mine field of the 3rd potash level. It was determined, that during the period from 1971 to 1980 a considerable part of the southern direction of the mine field on the area of more than 5,3 million m2 was mined by the roadways on the layers 2, 2–3, 3 without the mining of the 4th sylvinite layer. The volume of the leftover reserves of minerals in the mined panels makes more than 22 million tons. There is direct access to these panels from the main southern gates. As a study result of geological structure of the mined panels it was determined that under the influence of rock pressure the undermined sylvinite layer no. 4 took the form of a wave-shaped seam with the capacity of about 1 meter which rests on compressed inter-chamber pillars and on compressed rocks of layers 2, 2–3, 3 of destroyed inter-roadway pillars, which fills the space of the roadways. Such geological structure of the seam enables to extract minerals using the technology of selective layer mining by successive top and bottom faces. As a study result of the stability of the mine workings performed along the roadways and inter-chamber pillars under conditions of different roof positioning, it was determined that during the preparation of the faces the most advantageous locations for development workings are the areas previously mined by the room and pillar mining system. In this case, the highest stability of mine workings located in the stopes of the room and pillar mining system will be provided by their roofing location with cut of 0.15 m of the 4th sylvinite layer. When this occurs, their predicted life without repair, even without the use of special protection methods, would be between 3.5 and 8 years. Based on the results of the study, a conclusion was made on the technical possibility and economic feasibility of additional extraction of sylvinite ore reserves left in the western panels of the southern direction of the mine field of the 3rd potash level of the Production Unit no. 3 mine, finished over 40 years ago by the room and pillar mining system using selective layer mining technology by the longwall faces. With minimal capital, organizational and technical expenditures, the extraction of these reserves will allow the company to produce additionally 5.5 million tons of potash fertilizers.
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Eremin, Mikhail, Alexey Peryshkin, Gabriel Esterhuizen, Larisa Pavlova, and Victor Fryanov. "Numerical Analysis of Pillar Stability in Longwall Mining of Two Adjacent Panels of an Inclined Coal Seam." Applied Sciences 12, no. 21 (October 31, 2022): 11028. http://dx.doi.org/10.3390/app122111028.
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Longwall mining is one of the most widespread methods globally. During the preliminary development of the working, the coal seam is sectioned into panels divided by protective pillars. The pillars are necessary for maintaining the service life of underground mines, a highly productive stope, and personnel safety. In this work, we apply the finite-difference continuum damage mechanics approach to modeling the stress–strain evolution of the rock mass during the extraction of two adjacent longwall panels of an inclined seam. A new modification of the damage accumulation kinetic equation is proposed. The numerical-modeling approach accounts for an explicit number of numerous factors affecting the rock mass behavior. These factors are gravity forces, lithology, tectonic stresses, natural discontinuities, geotechnical, and mining parameters. When the model parameters are calibrated against the in situ observations, the results of the numerical-modeling approach provide a reliable basis for a pillar stability assessment. We build a structural model of a rock mass containing an underground working based on a simplified stratigraphy of the Kondomsky deposit, Kuznetsk coal basin, Russia. Based on the results of the numerical modeling, the stability of a pillar is analyzed. A new numerical technique extending the classical approach to the stability analysis is proposed and verified against the field data.
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Yang, Shi Jiao, Hui Luo, Jian Yong Dai, and Chang Zhen Wu. "Stability Analysis for Pillars during the Process of Panel Mining Based on Dynamic Fuzzy Reliability." Applied Mechanics and Materials 120 (October 2011): 263–68. http://dx.doi.org/10.4028/www.scientific.net/amm.120.263.
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Panel mining requires constructing lots of artificial pillars in underground metal mines. Along with the development of the mining process the stress-strain state of pillars changes constantly. Finite element numerical simulation with Midas/GTS software is used to analyze the stability of the pillar during the entire process of panel mining and consider randomness and fuzziness for material parameters of concrete and ore rock to get stress distribution in the pillar. In this paper, the performance function and equation of dynamic fuzzy reliability for a pillar in the whole mining process are established and are solved by a program developed with the MATLAB software. Applying the proposed theory and procedures to dynamic fuzzy reliability analysis and calculation of the pillar was set in panel mining under complex conditions in Zhao Tong Lead-Zinc mine. The results indicate that dynamic fuzzy reliability can better reflect the pillar stability during the entire process of panel mining and the proposed theory and procedures are effective in evaluating the dynamic fuzzy reliability.
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Zhang, Junwen. "Stability of Split-Level Gob-Side Entry in Ultra-Thick Coal Seams: A Case Study at Xiegou Mine." Energies 12, no. 4 (February 15, 2019): 628. http://dx.doi.org/10.3390/en12040628.
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Split-level longwall gob-side entry (SLGE) has been applied as a special form of small gate pillar mining (or non-coal pillar mining) in thick coal seams. The stability of the coal pillar directly affects the rationality of the layout of the SLGE. Starting from the mining-induced influence around the SLGE, this paper compares the mechanical properties of coal under different mining effects, and studies the rationality of “zero pillar” location against the Xiegou coal mine. The study shows that the key to success of the application of the SLGE is the existence of an intact zone within the triangular coal pillar in spite of double disturbances due to tunneling and coal mining extraction. Laboratory testing shows that the density and uniaxial compressive strength of rock specimens obtained from the triangular coal pillar are smaller than that from the other part of the panel which is concluded to be due to the varied degree of mining-induced influence. The numerical modeling results show that most of the triangular coal pillar is intact after extraction of the panel, and that the peak stress is located in the solid coal beyond the triangular coal pillar. The plastic zone of the triangular coal pillar is only about 1 m after the excavation of the tail gate of the next split-level panel. The physical modeling shows that the tail gate of the next panel is in the destressed zone with only a very small stress fluctuation during the extraction of the next panel. The study shows that the location of the SLGE at Xiegou coal mine is reasonable. SLGE is preferable for ultra-thick coal seams.
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Pongpanya, Phanthoudeth, Takashi Sasaoka, Hideki Shimada, and Sugeng Wahyudi. "Study of Characteristics of Surface Subsidence in Longwall Coal Mine under Poor Ground Conditions in Indonesia." Earth Science Research 6, no. 1 (January 31, 2017): 129. http://dx.doi.org/10.5539/esr.v6n1p129.
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This paper aims to study the characteristics of surface subsidence induced by longwall mining under poor ground conditions in Indonesia by means of numerical simulation techniques using finite difference code “FLAC3D”. The effect of mining depth in cases of single panel and multi-panel longwall mining, the influence of panel and pillar widths, and the impact of backfilling material, were incorporated into the FLAC3D software. The simulated results indicated that the angle of draw and maximum surface subsidence were significantly associated with the depth of mining, the number of extracted panels, the width of panel and pillar, and the type of backfill. In single panel mining, the largest maximum surface subsidence is observed in case of the shallowest mining depth, and it gradually decreases as the depth increases. In contrast, the angle of draw increases with increasing the mining depth. In multi-panel mining, the angle of draw and maximum surface subsidence increase as the mining depth increases. Moreover, the angle of draw and maximum surface subsidence decrease when the narrow panel and large pillar widths are adopted, and the backfilling materials are applied.
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Pongpanya, Phanthoudeth, Takashi Sasaoka, and Hideki Shimada. "PREDICTION OF MULTI-SEAM MINING-INDUCED SURFACE SUBSIDENCE IN UNDERGROUND COAL MINE IN INDONESIA." ASEAN Engineering Journal 12, no. 2 (June 1, 2022): 169–83. http://dx.doi.org/10.11113/aej.v12.17263.
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This paper attempts to predict the surface subsidence induced by multi-seam longwall mining in the PT Gerbang Daya Mandiri (GDM) underground coal mine in Indonesia. Several numerical models of multi-seam longwall mining under various depths were built in the finite difference code software “FLAC3D” which was used as a tool for numerical simulations. Effect of mining sequence and influence of lower seam mining were firstly investigated. The angle of draw (AoD) and maximum surface subsidence (Smax) were used to describe characteristics of the surface subsidence. Based on simulated results, it is indicated that the undermining provides a better mining sequence in multi-seam longwall mining compared to the overmining. Mining the coal seam in an undermining order will not cause any difficult mining conditions in a lower seam, whereas some ground control problems in an upper seam are expected when the coal seam is mined in an overmining order. Under all mining depths in the undermining, extracting the lower seam panels significantly influences the magnitude of surface subsidence. The AoD and Smax increase significantly after all panels in the lower seam is mined. This indicates that very large surface subsidence is expected when multi-seam mining is applied at GDM underground coal mine. An application of some countermeasures such as adopting a large pillar width and a small panel width is suggested in this underground coal mine in order to minimize the surface subsidence caused by multi-seam longwall mining. Minimizing the surface subsidence by adopting a large pillar width and a small panel width is therefore numerically investigated in this paper. Based on simulated results, it is found that the AoD and Smax decrease significantly when larger pillar width and narrower panel width are adopted. The use of larger pillar width and narrower panel width result in smaller AoD and Smax.
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Wang, Xu Feng, Dong Sheng Zhang, Ting Feng Cui, Jin Liang Wang, and Wei Zhang. "Study on Rational Width of Entry Protection Coal-Pillar in Large Mining Height Working Face." Advanced Materials Research 413 (December 2011): 404–9. http://dx.doi.org/10.4028/www.scientific.net/amr.413.404.
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This paper demonstrates the attempt to identify a reasonable chain pillar width in the condition of large mining height, along with a case study at the gateway of No.1103 panel with large mining height in Suancigou Mine. Theoretical calculation and numerical simulation were employed as the main approaches during the research to figure out the rational width of entry protection coal-pillar, which was then proved to be capable for engineering practice. The results that derived from our research can offer technical support for spot production, and serve as references for future investigation upon chain pillar design under large mining height.
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Cheng, Shixing, Zhanguo Ma, Peng Gong, Kelong Li, Ning Li, and Tuo Wang. "Controlling the Deformation of a Small Coal Pillar Retaining Roadway by Non-Penetrating Directional Pre-Splitting Blasting with a Deep Hole: A Case Study in Wangzhuang Coal Mine." Energies 13, no. 12 (June 15, 2020): 3084. http://dx.doi.org/10.3390/en13123084.
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In longwall mining of coal mines, the large deformation of small pillar retaining roadways creates difficulties for the safe and efficient retreating of the mining panel. Based on the engineering background of a small coal pillar retaining roadway in Wangzhuang coal mine, pressure relief technology for non-penetrating directional pre-splitting blasting with a deep hole ahead was proposed. The influence of the non-penetrating fracture length on the pre-splitting effect was studied by numerical simulation. The results showed that the vertical stress in the coal pillar center, the small pillar retaining roadway deformation, and the energy accumulation on the pillar decreased with an increase in the non-penetrating fracture length. The vertical stress at the working face end increased with an increase in the non-penetrating fracture length. The field application and monitoring results indicated that non-penetrating directional pre-splitting blasting could effectively control the deformation of small pillar retaining roadways. The roof-to-floor and rib-to-rib maximum convergences of the 6208 tail entry were reduced by 53.66% and 52.62%, respectively, compared to the results with no blasting. The roadway section met the demands of mining panel high-efficiency retreating, thereby demonstrating the rationality of the technical and numerical simulation results. The research results shed light on the improvement of small coal pillar retaining roadway maintenance theory and technology.
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Liu, Gui, Hua Xing Zhang, Jin Hui Chen, and Chao Gao. "The Optimization Research of Wide Strip and Full-Pillar Mining under Villages." Advanced Materials Research 616-618 (December 2012): 406–10. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.406.
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By making full use of the advantages of strip mining method and full-pillar mining method, the wide strip and full-pillar mining method can achieve the aim of mining under villages. However, at the full-pillar mining stage, the difficulty in managing several workfaces which are at work at the same time still exists. To improve the wide strip and full-pillar mining method’s applicability, an optimization of extraction sequence for coal pillars instead of the multi-working-face is put forward at the stage of full-pillar mining, and in the case of the deformation limit of surface structures is satisfied, to extract all the coal pillars which are under villages. By specific analysis of the extraction sequence optimization of the coal pillars in No.1 mine under Qian Xudapo village which belongs to Chang Chun coal Co., LTD., a better result is got which also acts a technological reference for the extraction under villages.
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Guo, Yanhui, and Yichen Miao. "Study on Stope Stability in Continuous Mining of Long-Dip, Thin Orebody by Room–Pillar Method." Sustainability 14, no. 15 (August 4, 2022): 9601. http://dx.doi.org/10.3390/su14159601.
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In order to analyze the stability of the stope under continuous mining with the room–pillar method for a kind of orebody with a long inclination, but not deep mining, this paper takes the room–pillar method for the continuous mining of a long-inclination orebody in the Mengnuo Lead–Zinc Mine, Yunnan Province as the research background. On the basis of the analysis of the stope mechanical model of a long, inclined, thin orebody with room-and-pillar mining, based on numerical simulation, the nature of the change in stress, displacement and the plasticity zone of the roof and pillar during continuous mining along the inclination are systematically analyzed. The results show that as the mining depth increases, the roof subsidence of the stope in the middle of the current operation increases. With the continuous mining of the lower middle section, the roof displacement of the stope will continue to increase with the subsequent mining of the middle section until the end of all stope operations, and the roof displacement of the stope has an obvious cumulative effect. The stress on the roofs and pillars increases with the gradual downward movement of the mining in each level, and the distribution of the plastic zone also expands. It shows that the stope structural parameters that are set according to shallow mining cannot fully meet the requirements of stability and safety in mining a deeper orebody. Therefore, for the mining of a non-deep orebody with a greater tendency to extend, the structural parameters of a shallow stope should not simply be used in the mining of a deeper orebody, but the pillar size should be appropriately increased or the spacing between the room and pillar should be reduced to ensure the stability and safety of the continuous stope.
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Putri, Ratih Hardini Kusuma. "Penentuan Lebar Chain Pillar Pada Tambang Batubara Shortwall Mining." Indonesian Mining Professionals Journal 2, no. 1 (November 28, 2020): 37–42. http://dx.doi.org/10.36986/impj.v2i1.21.
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Penambangan batubara dengan metode shortwall memiliki resiko terhadap keruntuhan atap lubang bukaan dan panel penambangan. Hal ini dipengaruhi oleh factor kestabilan dari lubang bukaan dan juga pilar sebagai penyangga alamiah pada area penambangan. Dengan adanya permasalahan tersebut diperlukan suatu kajian geoteknik terhadap rancangan pilar batubara bawah tanah, agar kegiatan penambangan dapat dikerjakan dengan aman dan lancar. Analisis kestabilan chain pillar menggunakan metode tradisional Obert dan Duvall (1967), dan Bienawski (1983).Penentuan desain lebar chain pillar dianalisis secara analitik. Berdasarkan acuan dalam penentuan rancangan pilar Hoek. E, Kaiser. P.K, dan Bawden.W.F., 1993, dengan ukuran lebar pilar, yaitu Safety Factor > 1.3.
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Kim, Jong-Gwan, Mahrous A. M. Ali, and Hyung-Sik Yang. "Robust Design of Pillar Arrangement for Safe Room-and-Pillar Mining Method." Geotechnical and Geological Engineering 37, no. 3 (October 27, 2018): 1931–42. http://dx.doi.org/10.1007/s10706-018-0734-1.
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Nikitin, O. "MINING BLOCK STABILITY PREDICTION BY THE MONTE CARLO METHOD." Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference 1 (June 26, 2006): 185. http://dx.doi.org/10.17770/etr2003vol1.2006.
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This paper analyses the stability of the mining blocks by the Monte Carlo method in Estonian oil shale mines, where the room-and-pillar mining system is used. The pillars are arranged in a singular grid. The oil shale bed is embedded at the depth of 40-75 m. The processes in overburden rocks and pillars have caused the subsidence of the ground surface. Visual Basic for Application was used for the modeling. Through Monte Carlo simulation, room-and-pillar stable parameters can be calculated. Model allows determination of the probability of spontaneous collapse of the pillars and surface subsidence by the parameters of registered collapsed mining blocks. Proposed method suits as an express-method for stability analysis and failure prognosis. It is applicable in different geological conditions, where the room-and-pillar mining system is used.
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Huang, Jing, Fanbao Meng, Ge Wang, Yingkui Wu, and Jinhao Wen. "Simulation Research for the Influence of Mining Sequence on Coal Pillar Stability under Highwall Mining Method." Geofluids 2021 (March 29, 2021): 1–9. http://dx.doi.org/10.1155/2021/8864339.
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Highwall mining, which is referred to the technique of extracting coal from the bottom of an exposed highwall, features safety, efficiency, and economy. According to existing highwall mining methods, the mining sequence has a great influence on highwall stability. Based on a highwall mining project in Australia, this study adopted the FLAC3D numerical simulation method to investigate the stability of coal pillars with different mining sequences. The results show that different mining sequences of boreholes exert a great effect on highwall stability. Compared with sequential mining, the skip mining method achieves higher speed of highwall stabilization and smaller plastic zone of coal pillar with its maximum strength decreasing by 12%. By adjusting the mining sequence scientifically, the coal pillar failure and roof collapse caused by the deviation of mining angle can be avoided. The results may provide a new angle for the studies on the coal pillar layout and stability design in highwall mining.
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Song, Wei Dong, Dong Xu Wang, and Ya Nan Tang. "Study on Sublevel Open Stoping with Subsequent Backfilling Mining Method Stope Parameters Optimization." Advanced Materials Research 250-253 (May 2011): 1567–71. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.1567.
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This paper discusses the stope parameters of the sublevel subsequent filling stage in Daye Iron Shizishan section. According to the similar material simulation technology, which is the main means, displacement monitoring and internal stress monitoring, several conclusions are summarized as bellow: When the parameter of the room and pillar is 18m, the underground mining is safe and steady. Impacts, which come from different regions’ mining, is different, and the greatest impact comes from the pillar’ mining. Stress monitoring shows that before roof fell down, there is a process of stress concentration. The stress in the roof is shear stress, and compressive stress in the pillar.
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Konicek, P., V. Kajzar, and J. Schreiber. "Seismic activity of hard coal longwall mining in protective shaft pillar near closed room and pillar panel." IOP Conference Series: Earth and Environmental Science 833, no. 1 (August 1, 2021): 012087. http://dx.doi.org/10.1088/1755-1315/833/1/012087.
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Wang, Bonan, Faning Dang, Wei Chao, Yanping Miao, Jun Li, and Fei Chen. "Surrounding rock deformation and stress evolution in pre-driven longwall recovery rooms at the end of mining stage." International Journal of Coal Science & Technology 6, no. 4 (November 12, 2019): 536–46. http://dx.doi.org/10.1007/s40789-019-00277-0.
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Abstract Two case studies were conducted in the Shennan mining area of Shaanxi Province, China to evaluate the surrounding rock deformation and stress evolution in pre-driven longwall recovery rooms. These studies mainly monitored the surrounding rock deformation and coal pillar stress in the recovery rooms of the N1206 panel of 2−2 coal seam at Ningtiaota Coal Mine and the 15205 panel of 5−2 coal seam at Hongliulin Coal Mine. The monitoring results showed that the surrounding rock deformation of the main recovery room and the coal pillar stress in the N1206 and 15205 panels began to increase significantly when the face was 36 m and 42 m away from the terminal line, respectively. After the face entered the main recovery room, the maximum roof-to-floor convergence in the N1206 and 15205 panels was 348.03 mm and 771.24 mm, respectively, and the coal pillar stresses increased more than 5 MPa and 7 MPa, respectively. In addition, analysis of the periodic weighting data showed that the main roof break position of the N1206 and 15205 panels after the longwall face entered the main recovery room was − 3.8 m and − 8.2 m, respectively. This research shows that when the main roof breaks above the coal pillar, the surrounding rock deformation of the main recovery room and the coal pillar stress increase sharply. The last weighting is the key factor affecting the stability of the main recovery room and the coal pillar; main roof breaks at disadvantageous positions are the main cause of the support crushing accidents.
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Li, Zhu, Guorui Feng, and Jiaqing Cui. "Research on the Influence of Slurry Filling on the Stability of Floor Coal Pillars during Mining above the Room-and-Pillar Goaf: A Case Study." Geofluids 2020 (September 12, 2020): 1–21. http://dx.doi.org/10.1155/2020/8861348.
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Room-and-pillar mining is a commonly used mining method in previous practice in northwest China mining area. Due to priority selection of high-quality resources, coal mines in northwest China generally have to face upward mining above goaf. Thus, the stability of a floor coal pillar influenced by mining activities plays an essential role in upward mining above goaf. The results indicated that a floor coal pillar kept stable before coal excavation in the no. 6107 working face in the Yuanbaowan coal mine; however, the plastic zone in the floor coal pillar expanded sharply and the elastic core zone reduced suddenly on the influence of abutment pressure. Finally, the floor coal pillar supported failure. Accordingly, the paper proposed a floor coal pillar reinforcing technique through a grout injection filling goaf area. As physically limited by a different-height filling body on the double sides, the plastic zone scope and horizontal displacement and loading capacity of the floor coal pillar were studied, working out that the critical height of the filling body should be about 6 m which can ensure safe mining when upward mining above goaf. Case practice indicated that the fractures induced by mining in the floor coal pillar, filling body, and floor can be restrained effectively when the filling body height is 6 m, which can ensure floor coal pillar stability and safe mining of the no. 6107 working face in the Yuanbaowan coal mine. The research can provide theoretical and technical guidance for upward mining above goaf and have a critical engineering practice value.
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Wang, Pengpeng, Yixin Zhao, Qingshan Ren, Yaodong Jiang, Cun Zhang, and Yirui Gao. "Floor Failure Characteristics in Deep Island Longwall Panel: Theoretical Analysis and Field Verification." Geofluids 2022 (March 17, 2022): 1–14. http://dx.doi.org/10.1155/2022/1851899.
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Floor failure in deep coal mining above confined aquifers with high-water pressure may induce floor water inrush disasters. Considering the effects of mining stress and nonuniformly distributed water pressure, a mechanical calculation model of the island longwall panel in up-dip mining was established, and the stress distribution and floor failure characteristics were analyzed. The failure characteristics of the floor at NO. 2129 panel in Xingdong coal mine were detected by the borehole televiewer and microseismic monitoring system to validate the theoretical model. The results indicated that the floor failure characteristics along the strike and inclination of the island longwall panel in up-dip mining were “asymmetric inverted saddle-shaped” and “spoon-shaped,” respectively. The maximum floor failure depths before and after roof hydraulic fracturing (RHF) were 45.7 m and 29.1 m, respectively. The theoretical calculation results of the maximum depths of floor failure were 45.1 m and 29.9 m, respectively. The theoretical failure characteristics were consistent with those measured on site. The stress concentration magnitude and floor failure depth on the side of the isolated coal pillar were greater than those of other areas, and the water-inrush-prone zones were concentrated on the side of the isolated coal pillar near the intersection of the working face and the roadway. The research results could provide a certain reference for floor failure and water inrush mechanisms under complex geological conditions in deep mining.
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Gong, Peng, Yongheng Chen, Zhanguo Ma, and Shixing Cheng. "Study on Stress Relief of Hard Roof Based on Presplitting and Deep Hole Blasting." Advances in Civil Engineering 2020 (October 26, 2020): 1–12. http://dx.doi.org/10.1155/2020/8842818.
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For the problem that the hard roof causes wider end-mining coal pillar, and the roadway is greatly affected by mining, this paper took Shanxi Luning Coal Mine as the engineering background; based on the stress distribution characteristics of the coal pillar, the calculation method of the limit end-mining coal pillar size was given; considering the formation conditions and transmission forms of the advanced abutment stress, a method combining presplitting and deep hole blasting was proposed to weaken the advanced abutment stress. The numerical simulation was used to analyze the stress distribution of coal pillars, which was verified by on-site industrial tests. The results showed that the presplitting can achieve the blocking of stress. The closer it is to the peak of the abutment stress, the better the blocking effect. Deep hole blasting can weaken the source of the advanced abutment stress and reduce the peak of abutment stress. With the combination of the two blasting methods, the end-mining coal pillar size of Luning Coal Mine can be reduced to 60 m. The method combining presplitting and deep hole blasting can effectively reduce the end-mining coal pillar size and reduce the impact of mining on the deformation of the dip roadway.
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Feng, Guorui, Songyu Li, Pengfei Wang, Jun Guo, Ruipeng Qian, Qiang Sun, Chenliang Hao, Xiaoze Wen, and Jianan Liu. "Study on Floor Mechanical Failure Characteristics and Stress Evolution in Double Predriven Recovery Rooms." Mathematical Problems in Engineering 2020 (April 21, 2020): 1–13. http://dx.doi.org/10.1155/2020/9391309.
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This paper takes the double predriven recovery rooms (DPRR) of 31109 panel of a coal mine in Inner Mongolia as a case study. DPRRs are used to withdraw mining equipment, which play a significant role in safe and efficient production in the final longwall mining stage. Theoretical analysis and numerical simulation were carried out to study the reasonable size of the front abutment pillar between DPRR (inter-DPRR pillar) and the damage depth of the DPRR floor. The results show that (1) the stress distribution of the fender (the remnant longwall panel) can be approximately divided into three stages with the advance of the working face: stress redistribution (the first) stage, stress superimposed growth (the second) stage, and stress transfer (the third) stage. (2) According to stress distribution and the corresponding failure mode of the fender, the calculation model of the slippage damage of the DPRR floor is rectified, and the damage range of the floor is rezoned to make it more suitable for the damage depth of the room. (3) The zone of influence of the front abutment pressure is 40–50 m, and the stress around the DPRR increases significantly in the final mining stage. When the size of the inter-DPRR pillar is greater than 15 m, the effect of increasing the coal pillar size on lowering the peak stress of the main predriven recovery room is limited. (4) Floor heave tends to increase at first and then decrease with depth and reaches the maximum in the depth of 5 m in the final mining stage, indicating that 5 m is the starting point for the initial depth of the floor heave. (5) The theoretical calculation shows that the reasonable size of the inter-DPRR pillar is 20 m, and the critical width of the fender is 18.48 m, which can guide the secondary support to prevent dynamic disasters. Floor grouting and constructing concrete floor are effective and economic ways to control the floor heave.
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Chen, Yang, Dong Li, Fuxing Jiang, Lili Zhang, Cunwen Wang, and Sitao Zhu. "Use of the Equivalent Mining Height Method for Understanding Overlying Strata Movement and Stress Distribution in an Isolated Coal Pillar." Shock and Vibration 2020 (October 10, 2020): 1–12. http://dx.doi.org/10.1155/2020/8820886.
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In order to study the changing rules of displacement filed and stress field of overlying strata on isolated pillar with filling mining method, a self-designed model of isolated pillar with an equivalent mining height and a monitoring system of stress is employed to study the progressive failure of overlying strata and the changing rules of induced displacement and stress, as the equivalent mining height increases. The findings from the trial tests show the following: (1) When the equivalent mining height is small, the overlying strata on the isolated coal pillar only bend and subside, but the overlying strata located on the goafs of two sides remain stable. (2) As the equivalent mining height increases, the degree of stress concentration on section coal pillar will rise and produce plastic failure in the first place near large caving goaf. The strata can subside between isolated working face and adjacent large caving goaf. (3) As the equivalent mining height increases further, new cracks in the roof of isolated working face will unite the cracks of carving goaf on two sides in horizontal direction, leading to a significant rise of the height of cracks. Three goafs will evolve into a large carving goaf, and the vertical cracks on the outer side of the carving goaf intersect with one another to form “fracture band”. The research acquires the key points for prevention in mining the isolated coal pillar with filling method and provides guidelines to implement this technique and to prevent rock burst.
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Feng, Rui Min, Jin Long Zhang, Hui Fu, and Lei Pei. "Research on the Design for Strip-Partial Mining Method under Villages at Xiaotun Colliery." Advanced Materials Research 361-363 (October 2011): 217–21. http://dx.doi.org/10.4028/www.scientific.net/amr.361-363.217.
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Basing on the geological mining condition under villages at Xiaotun Mine, according to the existing theories of the strip-partial mining, using the method of analyzing the field measurements date and calculating by empirical formula, the safe range of mining and retained widths can be confirmed, the mining schemes for different widths of coal pillar can be designed, and the optimum scheme can be worked out; and then the coal pillar stability of each mining scheme will be calculated through numerical simulation analysis, providing the basis for appropriately selecting the optimum scheme; on this basis, through simulation prediction of the surface movement and deformation, the surface movement and deformation laws of strip-partial mining is revealed to guide production of Xiaotun colliery.
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Wu, Quansen, Peng Kong, Quanlin Wu, Xinggang Xu, Xingyu Wu, and Tao Guo. "Study on Overburden Rock Movement and Stress Distribution Characteristics under the Influence of a Normal Fault." Advances in Civil Engineering 2020 (September 19, 2020): 1–16. http://dx.doi.org/10.1155/2020/7859148.
Full textAbstract:
Fault activation triggers local deformation and dislocation, releasing a large amount of energy that can easily cause mining disasters, such as rock bursts and roadway instability. To study the changing characteristics of overburden structures and the evolution law of mining-induced stress as panel advances towards a fault from a footwall, two similar models were established, namely, a simulation experimental model and a numerical simulation model. In addition, the relationship among mining, mining stress, and rock bursts induced by fault activation was investigated. The results of this study reveal that when the working face is 30 m away from the fault, the high-position rock mass near the fault turns to the goaf where the fault is activated, and the two walls display relatively obvious dislocation. During the process of footwall panel mining to the fault, the abutment stress of the coal pillar tends to increase initially, followed by a decrease. When the working face is 20 m away from the fault, the abutment stress ahead of the working face reaches its maximum. When the width of the coal pillar is within the range of 10–40 m, the coal pillar accumulates a large amount of energy, and the working face affected by the fault easily induces a rock burst. Before fault activation, disturbances arising from the mining activities destroy the equilibrium stress environment of the rock system surrounding the fault, and the fault continuously accumulates energy. When the accumulated energy reaches a certain threshold, under the action of normal stress or shear stress, the fault will be activated, and a large amount of energy will be released, which can easily induce a rock burst. The research results in this paper provide a scientific basis for the classification, prediction, and prevention of rock bursts under similar geological conditions.
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Fan, Yuan, Wei Dong Pan, Zhao Hui Wang, De Lin Li, and Wen Bo Song. "Narrow Pillar Mining Technology of Fully Mechanized Sublevel Caving Faced with Great Cutting Height in Tashan Mine." Applied Mechanics and Materials 295-298 (February 2013): 2950–53. http://dx.doi.org/10.4028/www.scientific.net/amm.295-298.2950.
Full textAbstract:
Based on the great thickness of coal seam in Tashan Mine, narrow pillar mining technology was adopted to liberate more coal resources from coal pillars. In this paper, the research status of narrow pillar technology was analyzed, and the main problems of the narrow pillar mining technique were solved by theory research. The method and technical route of this study was offered in final. The results have great reference value to the fully mechanized sublevel caving with great mining height in similar conditions.
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Guo, Yuxia, Honghui Yuan, Xiaogang Deng, Yujiang Zhang, Yunlou Du, Hui Liu, Guorui Feng, Jiali Xu, Renle Zhao, and Dao Viet Doan. "A Method for Determining Feasibility of Mining Residual Coal above Out-Fashioned Goaf under Variable Load: A Case Study." Advances in Civil Engineering 2020 (August 27, 2020): 1–12. http://dx.doi.org/10.1155/2020/8837657.
Full textAbstract:
Out-fashioned goaf is the protective structure for mining the upper residual coal, and its stability is the core problem in mining the upper residual coal. According to the upward mining demand for No. 5 coal seam above the out-fashioned goaf in Baizi Coal Mine, a new method is proposed to determine the upward mining safety. According to the analysis of the actual situation of the mine, the coal pillar and suspended roof in the out-fashioned goaf are taken as the objects. Furthermore, a “coal pillar-suspended roof” system model based on the variable load induced by abutment pressure of upper coal seam mining is established. After the mechanical model was solved, the parameter acquisition method of the model was established. The basic parameters of Baizi Coal Mine were considered to determine the feasibility of mining residual coal above out-fashioned goaf. And the effects of variable load on the coal pillar and suspended roof stability were analyzed. The results show that the upper No. 5 coal seam in Baizi Coal Mine can be mined safely. Compared to the traditional method, which simplifies all the upper loads to uniform loads, the new method is safer. The system stability of the suspended roof and coal pillar is influenced by “a/L” and “L.” Axial stress curves of the coal pillar and suspended roof appear nearly parabolic with “a/L” varying. Their maximum values are obtained when the “a/L” value is around 0.5∼0.6. In this situation, the combination structure is most easy to to be damaged. The ratio q′/q has a linear relationship with all stresses of the system model. The failure sequence of the system model is determined by analyzing the relationship between the tensile strength of the suspended roof and compressive strength of the coal pillar. This study provides a reference case for coal resources upward mining under similar conditions.
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Pan, Ruikai, Yong Li, Hui Wang, Youlin Xu, and Hongyun Yang. "Assessment of ground instability risk of lower seam longwall panels during crossing overlying remnant pillars." Royal Society Open Science 7, no. 10 (October 2020): 201249. http://dx.doi.org/10.1098/rsos.201249.
Full textAbstract:
One of the most challenging safety problems is ground instability during crossing overlying remnant pillars (CORP). Ground instability not only causes injury to miners or fatalities, but also leads to interruptions in the mining operations and breakdowns in equipment. In this paper, 12 major parameters influencing the ground instability were firstly determined based on extensive international experience associated with CORP. The consequences of the ground instability were then assessed in terms of miners' health and financial losses. Afterwards, a practical method to assess the ground instability risk of lower-seam longwall panels during CORP was developed based on its probability and consequence. Finally, this method was successfully used to determine the best scheme for CORP of LW10-103 at Mugua coal mine. The main advantage of this method is that it enables mining engineers to easily use international experience for assessing the risk of ground instability and selecting reasonable supports during CORP.
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Shao, Xiao Ping, and Yu Cheng Xia. "Modeling and Numerical Optimal Simulation of Coal Pillar’s Failure Process on Longwall Leaving Coal Pillar Mining." Applied Mechanics and Materials 88-89 (August 2011): 285–90. http://dx.doi.org/10.4028/www.scientific.net/amm.88-89.285.
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To further optimize mining methods and parameters at regions of “protecting water mining”, this paper has made modeling and numerical optimal simulation of coal pillar’s failure process under two kinds of mining method including “taking 8 remaining 7” leaving the region pillars and “taking 12 remaining 8” leaving strip coal pillars for Yubojie coal mine in northern Shaanxi province in China. Simulation showed that the stability of strip coal pillars is better than the region coal pillars at the same advancing distance. The region coal pillars first appeared corner plastic failure and maybe become hexagonal pillars. Plastic failure of the rectangular pillar extended and penetrated from the corner along the edge. Plastic damage of pillars showed tendency from the middle to the roadway side of the face along the length direction of face. Stability of central elastic core of coal pillar is the basis of pillar stability. Simulation results showed that it is feasible to optimize mining methods and parameters of “protecting water mining" areas based on modeling and numerical simulation of pillar failure process. The method has provided a useful reference to mining method and optimization design research for other regions with same type of domestic and international coal mines.
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Guo, Qi Feng, Zhao Cai Zhang, Zheng Sheng Li, Kun Liu, and Huan Xin Liu. "Mining Method Optimization Based on Fuzzy Comprehensive Evaluation." Advanced Materials Research 616-618 (December 2012): 365–69. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.365.
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According to the 8000t/d production capacity planning and high in-situ stress, high rockburst proneness in deep mining of Sanshandao Gold Mine, three mining methods were compared and analyzed from safety, technical and economic indexes. Fuzzy optimization model was built to select the optimal mining method based on mining indexes quantification and fuzzy analysis of mining indexes. The conclusion shows that Alternate Room-Pillar Mining Method with Ascending Backfill is the optimal mining method to satisfy the safety and high efficiency demand of deep mining in Sanshandao Gold Mine.
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Wei, Ke Min, Mao Sen Zhao, Ze Kang Wen, and You Ling Fang. "Distribution of Underground Pressure Law and Fracture Zone Prediction Research of Overburden in Steep and Multiple Coal Seams Mining." Applied Mechanics and Materials 448-453 (October 2013): 3888–92. http://dx.doi.org/10.4028/www.scientific.net/amm.448-453.3888.
Full textAbstract:
Use Taiping coal mines second horizontal (+1100m~+900 m level ) 1#, 3# and 5# coal seam in Panzhihua Baoding as the research object, apply the problem solving nonlinear large deformation finite difference method (FLAC), to research the steep multi-seam mining of pressure distribution and characteristics of fracture zone. The results show that: (1)During the course of three coal mining extraction, the stress of goaf surrounding rocks will be changed. (2)When the nearby coal is mining, the coal pillar come into being stress concentration near the area. when the mining work continues, the goaf will have an effect on the protection pillar, which is similar to the "liberate". the effect of coal pillar and stress concentration nearby will be eased; (3)After the coal mining, plastic failure has occurred over the protection pillar, forming a water guide channel. Research results can be as a reference for similar steep seam mining.